Noncontact power transmission apparatus and power transmission device

ABSTRACT

A noncontact power transmission apparatus includes an instrument including a first case, a power reception coil arranged to generate an induced current due to magnetic flux in a first direction intersecting a gravitational direction, and a holder configured to hold the power reception coil at a predetermined distance from an outer surface of the first case in the first case. A power transmission device includes a conductive second case that has an opening into which the instrument is inserted in which the instrument is stored, a power transmission coil provided in the second case so as to generate magnetic flux in the first direction, and disposed to generate an induced current in the power reception coil, and an elastic body that is provided in the second case, maintains a distance between the power transmission coil and the power reception coil to be constant, and supports the power transmission coil.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to Japanese PatentApplication No. P2017-057961, filed Mar. 23, 2017, the entire contentsof which are incorporated herein by reference.

FIELD

Exemplary embodiments described herein relate to a noncontact powertransmission apparatus used for an instrument such as a portablethermosensitive recording apparatus.

BACKGROUND

A portable terminal apparatus such as a smart phone has a secondarybattery which is chargeable and built thereinto. A charging AC adaptoris connected to the portable terminal apparatus in a wired manner, andcharges the secondary battery. In recent years, a noncontact chargingfunction has been installed in a portable terminal apparatus. Theportable terminal apparatus includes a power reception coil receivingpower, a power reception circuit generating power through the powerreception coil, a charging circuit charging a secondary battery, and thelike, and thus realizes a noncontact charging function. The noncontactcharging function applies noncontact power transmission in which poweris transmitted from a power transmission coil in a noncontact manner,and the power is received by a power reception coil.

Regarding the noncontact power transmission, a method is widely used inwhich power is transmitted through electromagnetic induction between apower transmission coil provided in a power transmission device and apower reception coil provided in a portable terminal apparatus. Afrequency bandwidth used for electromagnetic induction is about 100 kHzto 200 kHz. A charging stand has a noncontact power transmissionfunction. A surface of the portable terminal apparatus is planar, andthus a surface of the charging stand, which is a power transmissiondevice on which the portable terminal apparatus, is placed is alsoplanar. If the portable terminal apparatus is placed at any position onthe surface of the charging stand, the charging stand detects a positionof the portable terminal apparatus, moves the power transmission coilsuch that the power transmission coil and the power reception coil havean optimal positional relationship, and then charges the portableterminal apparatus. Fine position adjustment is further performed duringcharging, and thus power transmission efficiency is increased.

The use of a noncontact charging apparatus is not limited to a portableterminal apparatus such as a smart phone having a thin shape. Even in aportable terminal apparatus or an electronic instrument having someextent of thickness, and further having a protrusion, a secondarybattery built into the portable terminal apparatus or the electronicinstrument can be charged by using the noncontact charging apparatus.For example, a noncontact charging apparatus is used in a box-shapedportable electronic instrument such as a portable printer or a portablevideo camera, or a toy. A charging stand collectively charges aplurality of such instruments.

In a case where power is sent to an electronic instrument throughnoncontact power transmission, noise tends to be generated in a powertransmission device or a power reception device. In order to suppressnoise generated in the power transmission device and the power receptiondevice, the power transmission device and the power reception device aresurrounded by a metallic box. In order to increase power transmissionefficiency, a power transmission coil built into the power transmissiondevice and a power reception coil built into the power reception deviceare required to be maintained at positions separated from each other bya predetermined distance. In a case where the power transmission deviceand the power reception device are surrounded by the metallic box, it ishard to check whether or not the devices are held to be separated fromeach other by a predetermined distance from the outside of the box.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a noncontact power transmission apparatusaccording to a first exemplary embodiment.

FIG. 2 is an exterior diagram of a portable thermosensitive recordingapparatus according to some embodiments.

FIG. 3 is a diagram illustrating the inside of the portablethermosensitive recording apparatus according to some embodiments.

FIG. 4 is a diagram illustrating a recording unit of the portablethermosensitive recording apparatus and thermosensitive recording paperaccording to some embodiments.

FIG. 5 is an exterior diagram of a charging box.

FIG. 6 is a diagram illustrating an internal configuration of thecharging box.

FIG. 7 is a sectional view illustrating an internal configuration of thecharging box.

FIG. 8 is a flowchart illustrating control during noncontact charging.

FIG. 9 is a graph illustrating a relationship between a distance betweena power transmission coil and a power reception coil, and receivedpower.

FIG. 10 is a diagram illustrating a noncontact power transmissionapparatus according to a second exemplary embodiment.

FIG. 11 is a diagram illustrating a noncontact power transmissionapparatus according to a third exemplary embodiment.

DETAILED DESCRIPTION

A noncontact power transmission apparatus of some embodiments includesan instrument including a first case, a power reception coil that isdisposed to generate an induced current due to magnetic flux in a firstdirection intersecting a gravitational direction, and a holding unitthat holds the power reception coil at a predetermined distance from anouter surface of the first case in the first case; and a powertransmission device including a conductive second case that has anopening into which the instrument is inserted, and stores theinstrument, a power transmission coil that is provided in the secondcase so as to generate magnetic flux in the first direction, and isdisposed to generate an induced current in the power reception coil, andan elastic body that is provided in the second case, maintains adistance between the power transmission coil and the power receptioncoil to be constant, and supports the power transmission coil.

Hereinafter, exemplary embodiments will be described with reference tothe drawings. The same reference numeral indicates the same constituentelement in the drawings.

A noncontact power transmission apparatus is formed of a powertransmission device, and an instrument including a power receptiondevice. In the present exemplary embodiment, a portable thermosensitiverecording apparatus is exemplified as the instrument. The portablethermosensitive recording apparatus may be a small printing apparatuswhich is easily carried. Hereinafter, detailed description thereof willbe made.

First Exemplary Embodiment

As illustrated in FIG. 1, a noncontact power transmission apparatus 100is formed of a power transmission device 110, and a power receptiondevice 130 provided in an instrument 120. FIG. 1 is a block diagramillustrating a circuit configuration of the power transmission device110 and the power reception device 130. The instrument 120 may be aportable thermosensitive recording apparatus. The portablethermosensitive recording apparatus 120 includes a charging unit 152which is supplied with power from the power transmission device 110 andcharges a secondary battery 153 in a noncontact manner.

The power transmission device 110 is connected to an AC power source of100 V via a plug 111. The power transmission device 110 includes an ACadaptor 112, a power transmission unit 113, a power transmission sidecontrol unit 114, a sensor 115, and a display unit 116.

The AC adaptor 112 converts AC power which is input via the plug 111into DC power. The DC power is used to drive the power transmission sidecontrol unit 114 and the power transmission unit 113. The powertransmission unit 113 is a circuit generating transmission power whichis required to transmit power to the power reception device 130. Thepower transmission side control unit 114 includes a microcomputercontrolling the power transmission device 110, and an oscillationcircuit generating a power carrier for power transmission. Themicrocomputer may be formed of a central processing unit (CPU), a randomaccess memory (RAM), a read only memory (ROM), and a circuit providedwith input/output (I/O) ports. A frequency of a carrier for noncontactpower transmission is 6.78 MHz. The sensor 115 is a limit switch, apressure sensor, or the like. The sensor 115 detects a distance betweenthe power transmission device 110 and the power reception device 130.The display unit 116 is a light emitting diode (LED) or a liquid crystalpanel. In a case where the power reception device 130 is placed at anappropriate position for the power transmission device 110 on the basisof a detection result in the sensor 115, the LED is lit. In a case wherecharging of the secondary battery built into the power reception device130 is completed, the LED is turned off. In a case where the powerreception device 130 becomes distant from the power transmission device110, the LED blinks. The power transmission unit 113 is connected inseries to a power transmission capacitor 117 and a power transmissioncoil 118. A resonance circuit formed of the power transmission capacitor117 and the power transmission coil 118 generates AC power with afrequency which is the same as or substantially the same as aself-resonance frequency.

As a frequency of AC power generated by the power transmission device110, a frequency of about 100 kHz is used in a case where anelectromagnetic induction method is used for power transmission, and afrequency of several MHz to several tens of MHz is used in a case wherea magnetic field resonance method is used for power transmission. In acase of the magnetic field resonance method, a frequency of 6.78 MHz or13.56 MHz is frequently used. In the present exemplary embodiment, afrequency of 6.78 MHz may be used. In the present exemplary embodiment,an operation frequency is not limited, and a wide frequency bandwidth ina case of an electromagnetic induction method, a magnetic fieldresonance method, or the like can be used.

In order to transmit power with high accuracy, the power transmissionunit 113 is formed of a class-D amplification circuit with a switchingcircuit. A switching element used in a switching circuit is formed of ametal-oxide-semiconductor field effect transistor (MOSFET). A class-Eamplification circuit may be used instead of the class-D amplificationcircuit. A gallium nitride FET (GaN FET) may be used in order to performhigh frequency switching instead of the MOSFET.

The instrument 120 includes the power reception device 130 receivingpower transmitted from the power transmission device 110, and a loadsection 150 which is operated by using received power. In the presentexemplary embodiment, the load section 150 is formed of a secondarybattery and a portable recording device including the secondary battery.

The power reception device 130 is a part of the portable thermosensitiverecording apparatus (instrument) 120. The power reception device 130includes a resonance circuit formed of a resonance capacitor 131 (powerreception capacitor) and a resonance coil 132 (power reception coil)connected in series to each other, a rectification unit 133, a voltageconversion unit 134, a power reception side control unit 151, thecharging unit 152, and the secondary battery 153. The power receptionside control unit 151, the charging unit 152, and the secondary battery153 also form the load section 150 of the portable thermosensitiverecording apparatus (instrument) 120. The load section 150 furtherincludes a secondary battery load unit 154. The secondary battery loadunit 154 includes a thermosensitive recording head 160, a paper carryingportion 161, and a display portion 162.

The power reception capacitor 131 and the power reception coil 132connected in series to each other in the power reception device 130 areset to values causing resonance at 6.78 MHz. An electromagnetic wavesent via the resonance circuit formed of the power transmissioncapacitor 117 and the power transmission coil 118 of the powertransmission device generates an induced current in the power receptioncoil 132, and thus resonance occurs in the power reception capacitor 131and the power reception coil 132. Power is generated due to theresonance in the power reception device. The power reception capacitor131 and the power reception coil 132 are connected to the rectificationunit 133. The rectification unit 133 converts an AC transmitted at 6.78MHz into a DC. The voltage conversion unit 134 converts a voltageconverted into the DC in the rectification unit 133, into a voltage fordriving each unit of the load section 150.

The power reception side control unit 151 controls the charging unit152, the thermosensitive recording head 160, the paper carrying portion161, and the display portion 162. The charging unit 152 charges thesecondary battery 153 with power obtained from the voltage conversionunit 134. The power obtained through the power reception capacitor 131and the power reception coil 132 is used for an operation of the powerreception side control unit 151, and is also used for charging of thesecondary battery 153 and operations of the thermosensitive recordinghead 160, the paper carrying portion 161, and the display portion 162.

A self-resonance frequency of the resonance circuit formed of the powerreception coil 132 and the power reception capacitor 131 of the powerreception device 130 is the same as or substantially the same as aself-resonance frequency of the resonance circuit formed of the powertransmission coil 118 and the power transmission capacitor 117 of thepower transmission device 110. The frequencies are the same as eachother, and thus power is efficiently transmitted from the powertransmission side to the power reception side through electromagneticcoupling.

FIG. 2 illustrates an exterior of the portable thermosensitive recordingapparatus 120. FIG. 3 shows the portable thermosensitive recordingapparatus 120 taken along the line III-III in FIG. 2. FIG. 3 illustratesa case where the power reception coil 132 is fixed to a case 170. FIG. 4illustrates a state in which a cover 179 of the portable thermosensitiverecording apparatus 120 is opened. Rolled paper 182 is thermosensitiverecording paper with a width of 50 mm, and is stored in the case 170.The portable thermosensitive recording apparatus 120 corresponds to theinstrument 120 illustrated in FIG. 1, and includes the power receptiondevice 130 and the load section 150.

In FIG. 2, a Z axis indicates a gravitational direction. The exterior ofthe case 170 has a height H1 (120 mm) in a Z axis direction, a width W1(90 mm) in a Y axis direction, and a depth D1 (70 mm) in an X axisdirection. The portable thermosensitive recording apparatus 120 includesthe cover 179 on an upper side in the X axis direction. The cover 179 isalso used as a discharge port 171 for the printed thermosensitiverecording paper 182. A power switch 172, a paper feed switch 173, and apause switch 174 are provided on a front surface in the Z axisdirection. The secondary battery 153 can be inserted into the case 170from a side surface in the Y axis direction. The power reception coil132 is provided inside the portable thermosensitive recording apparatus120.

FIG. 3 illustrates a state in which the portable thermosensitiverecording apparatus 120 illustrated in FIG. 2 is divided into an upperpart 180 and a lower part 181 along the line III-III. A printed circuit(PC) board 176 on which a pattern of the power reception coil 132 isformed is provided in the lower part 181 of the case 170. The PC board176 may be formed of a glass epoxy board. The pattern of the powerreception coil 132 is formed by using copper foils on the PC board 176.The power reception coil 132 may be formed in a square spiral pattern oftwo turns with a height H2 (60 mm) and a width W2 (45 mm). The PC board176 may be held at the case 170 with screws 175. The power receptioncoil 132 is provided to be parallel to a bottom 187 at a positionseparated from an end of the case 170 by a distance D2 (6 mm). When theportable thermosensitive recording apparatus 120 is placed on an X-Yplane, the power reception coil 132 is provided to be parallel to a Y-Zplane. In a case where the power reception coil 132 is disposed to beparallel to the Y-Z plane, and receives magnetic flux in the X axisdirection, an induced current is generated. In other words, the powerreception coil 132 receives magnetic flux in the direction perpendicularto the gravitational direction so as to generate an induced current. Aninduced current with 6.78 MHz may be generated by the power receptioncoil 132 and the power reception capacitor 131.

A pattern end of the power reception coil 132 is connected to a circuit177 including the power reception capacitor 131 and the rectificationunit 133. The voltage conversion unit 134 is disposed in the upper part180, and is electrically connected to the power reception side controlunit 151 and the charging unit 152.

FIG. 4 illustrates a state in which the cover 179 of the portablethermosensitive recording apparatus 120 is opened. The cover 179 isopened, and the wound thermosensitive recording paper 182 is insertedinto a paper holding unit 183 of the case 170. The portablethermosensitive recording apparatus 120 includes the thermosensitiverecording head 160 performing printing on thermosensitive paper, and thepaper carrying portion 161 feeding the thermosensitive recording paper182 to the thermosensitive recording head 160. The paper carryingportion 161 includes a gear 184 which is rotated by a motor (notillustrated), a gear 185 engaged with the gear 184, and a platen roller186. The platen roller 186 is rotated by the gear 185, and thusthermosensitive paper is carried. The power reception side control unit151 controls the thermosensitive recording head 160 to perform printingon the thermosensitive paper carried thereto according to printing data.

FIG. 5 illustrates a charging box 200 which is mounted with the powertransmission device 110 and transmits power in a noncontact manner. Thecharging box 200 is surrounded by case surfaces 201A, 201B, 201C, 201Dand 201E. Each of the case surfaces (201A to 201E) may be formed of astainless plate with a thickness of 0.1 mm. A part of the charging box200 is formed as an opening 201 storing the portable thermosensitiverecording apparatus 120. The case surface 201A is a front surface, thecase surfaces 201B and 201C are side surfaces, the case surface 201D isa mounting surface of the charging box 200, and the case surface 201E isan inner surface (rear surface). A case 203 made of stainless steel isprovided on the case surface 201E, and the power transmission device 110is provided in the case 203. A PC board 204 is mounted with circuitcomponents of the power transmission device 110 and the powertransmission capacitor 117. The AC adaptor 112 is externally attached.An exterior of the charging box 200 may have a height H3 (150 mm) in theZ axis direction, a width W3 (150 mm) in the Y axis direction, and adepth D3 (140 mm) in the X axis direction. The charging box 200 has ashape into which the portable thermosensitive recording apparatus 120 iseasily inserted. LEDs 205A and 205B are provided on the case surface201A which is the upper surface of the charging box 200. The LEDs 205Aand 205B are disposed at both ends near the opening 201 in the Y axisdirection.

The charging box 200 is made of a highly conductive metal material inorder to prevent leakage of an electric wave. As a metal material, notonly stainless steel but also aluminum or copper may be used.

FIG. 6 illustrates the charging box 200 disposed on a mounting surface240, and the portable thermosensitive recording apparatus 120 insertedinto the charging box 200 for noncontact charging. For betterunderstanding of an internal configuration of the charging box 200,parts of the case surfaces 201A and 201C are removed. The powertransmission coil 118 is disposed on the case surface 201E side insidethe charging box 200. The power transmission coil 118 is formed in acopper foil pattern on a PC board 210 made of glass epoxy, and is aplanar coil. The power transmission coil 118 may be formed in a squarespiral pattern of two turns with a height H4 (60 mm) in the Z axisdirection and a width W4 (55 mm) in the Y axis direction. A height H5 ofthe power transmission coil 118 in the Z axis direction from themounting surface 240 is substantially the same as a height H6 of thepower reception coil 132 of the portable thermosensitive recordingapparatus 120 from the mounting surface 240. Each of the heights H5 andH6 is 20 mm. An end of the pattern of the power transmission coil 118 isconnected to the power transmission capacitor 117 via a wiring 206.

The power transmission coil 118 may be formed in the pattern of twoturns having the height H4 and the width W4, and the power receptioncoil 132 is formed in the pattern of two turns having the height H2 andthe width W2. The heights H4 and H2 are set to the same value, and avalue of the width W4 is greater than a value of the width W2. When theportable thermosensitive recording apparatus 120 is inserted into thepower reception box 200, the center of the power transmission coil 118and the center of the power reception coil 132 may undergo a slightlypositional deviation in the Y axis direction. Since the width W4 is setto a value greater than a value of the width W2, even in a case where apositional deviation occurs in the Y axis direction, power can be sentfrom the power transmission coil 118 to the power reception coil 132 ina state in which power transmission efficiency is maintained.

A spring 220 is provided between the case surface 201E and the PC board210 on which the pattern of the power transmission coil 118 is formed.One end of the spring 220 is fixed to the PC board 210 so as to pressthe substantial center of the power transmission coil pattern formed onthe PC board 210 in the direction of the opening 201. The other end ofthe spring 220 is fixed to the case surface 201E such that a centralline of the spring 220 is substantially parallel to the case surface201D. The spring 220 supports the PC board 210 in a swingable manner. Ina case where the portable thermosensitive recording apparatus 120 isinserted into the charging box 200, the portable thermosensitiverecording apparatus 120 is butted against the PC board 210 via a spacer232. Even if the portable thermosensitive recording apparatus 120 isinserted in a slightly inclined manner, the PC board 210 is buttedagainst the portable thermosensitive recording apparatus 120 by thespring 220. As a result, the power reception coil 132 and the powertransmission coil 118 can be caused to face each other in parallel toeach other while a predetermined distance therebetween is maintained.

The spring 220 is an elastic body such as a coil spring or a platespring. A rubber may be used as another elastic body. The spring 220 hasa selected predetermined spring constant. The spring constant isselected to generate force enough to move the power transmission coil118 to the opening 201 side in a case where the portable thermosensitiverecording apparatus 120 is not put, and is selected to generate forceenough not to move the portable thermosensitive recording apparatus 120in a case where the portable thermosensitive recording apparatus 120 isput.

Position detection sensors 230A and 230B are provided between the PCboard 210 and the case surface 201E of the charging box 200. Theposition detection sensors 230A and 230B are disposed at both ends inthe Y axis direction inside the charging box 200. Each of the positiondetection sensors 230A and 230B is the same limit switch. The portablethermosensitive recording apparatus 120 is inserted into the chargingbox 200 so as to be in pressure contact with the PC board 210. Theposition detection sensors 230A and 230B detect a position of the PCboard 210. In other words, positions of the power transmission coil 118and the power reception coil 132 are detected. The sensors 230A and 230Bare turned on when the sensors 230A and 230B are brought into contactwith the PC board 210, and are turned off when the sensors are separatedfrom the PC board 210.

FIG. 7 illustrates sections of the portable thermosensitive recordingapparatus 120 and the charging box 200. The spacer 232 is provided onthe PC board 210 on the opening 201 side. The spacer is made of a resin,and has a thickness (D5) of 12 mm, and a height (H7) of 40 mm. The PCboard 210 has a thickness (D6) of 2 mm. The portable thermosensitiverecording apparatus 120 is inserted from the opening 201 and is pusheduntil being brought into contact with the spacer 232. The spacer 232 isbrought into contact with a surface (a height (H8) of 45 mm) of theportable thermosensitive recording apparatus 120, and thus the spring220 is contracted. Consequently, a distance D4 between the powertransmission coil 118 and the power reception coil 132 is maintained tobe constant. The distance D4 is set to 20 mm. The spacer 232 is incontact with the case of the portable thermosensitive recordingapparatus 120 such that the distance D4 is maintained at an appropriatevalue.

As illustrated in FIG. 6, in a case where the portable thermosensitiverecording apparatus 120 is put into the charging box 200 so as to bebutted against the power transmission coil 118, and is then furtherpressed inward, the PC board 210 on which the power transmission coil118 is formed is moved toward the inner surface. If the portablethermosensitive recording apparatus 120 reaches the position detectionsensors 230A and 230B, states of the sensors 230A and 230B are switched.When the states of the sensors 230A and 230B are switched, the powertransmission coil 118 and the power reception coil 132 are located atappropriate positions with the spacer 232 interposed therebetween, andmutually apply force to each other due to the spring 220. The powertransmission side control unit 114 lights the LEDs 205A and 205B so asto show to the outside of the charging box 200 a state in which thepower transmission coil 118 and the power reception coil 132 arechargeable. In other words, lighting of the LEDs 205A and 205B indicatesthat the portable thermosensitive recording apparatus 120 is located ata chargeable position. After the LEDs 205A and 205B are lit, powerstarts to be transmitted from the power transmission coil 118 to thepower reception coil 132. In the present exemplary embodiment, a singleLED may indicate that the portable thermosensitive recording apparatus120 is located at a chargeable position instead of the two LEDs 205A and205B.

FIG. 8 is a flowchart illustrating that the power transmission sidecontrol unit 114 of the charging box 200 controls the power transmissiondevice 110 so as to start power transmission (charging). As illustratedin FIGS. 6 and 7, the charging box 200 has a configuration in which thesensors 230A and 230B detecting a position of the PC board 210 on whichthe power transmission coil 118 is formed are respectively provided onthe left and right of the inside.

If power is supplied to the charging box 200 from the AC adaptor 112,the display unit (LEDs 205A and 205B) is controlled to normally blink atan interval of 10 seconds (ACT 100). In ACT 110, the power transmissionside control unit 114 operates the sensors 230A and 230B. The portablethermosensitive recording apparatus 120 is inserted into the chargingbox 200, and the portable thermosensitive recording apparatus 120 isbutted against the PC board 210. In a case where the PC board 210 turnson the sensor 230A (YES in ACT 120), it is subsequently detected whetherthe sensor 230B is turned on or off (ACT 130). In a case where thesensor 230B is turned on (YES), the sensors 230A and 230B are turned on,and the power transmission side control unit 114 determines that thepower transmission coil 118 and the power reception coil 132 are locatedat positions suitable for noncontact power transmission. In other words,a distance between the power transmission coil 118 and the powerreception coil 132 is the distance D4. Next, blinking of the LEDs 205Aand 205B is stopped, and the LEDs 205A and 205B are lit (ACT 140).Lighting of the LEDs 205A and 205B indicates that noncontact powertransmission can be performed. Power starts to be transmitted from thepower transmission coil 118 to the power reception coil 132 according tothe lighting of the LEDs 205A and 205B (ACT 150). The portablethermosensitive recording apparatus 120 charges the secondary battery153 built thereinto through the noncontact power transmission.

On the other hand, in a case where the sensor 230A does not detect thePC board 210 (NO in ACT 120), the power transmission side control unit114 detects a state of the sensor 230B (ACT 160). In a case where thesensor 230A does not detect the PC board 210, and the sensor 230Bdetects the PC board 210 (YES in ACT 160), the power transmission sidecontrol unit 114 causes the LED 205A to blink at a time interval of 0.5seconds. In a case where the sensor 230A detects the PC board 210, andthe sensor 230B does not detect the PC board 210 (NO in ACT 130), thepower transmission side control unit 114 causes the LED 205B to blink ata time interval of 0.5 seconds. In a case where the LEDs 205A and 205Bblink in a long cycle (interval of 10 seconds), this indicates that thecharging box 200 is in a standby state for charging the portablethermosensitive recording apparatus 120. In a case where the LEDs 205Aand 205B blink in a short cycle (an interval of 0.5 seconds), thisindicates a state in which the portable thermosensitive recordingapparatus 120 is obliquely inserted into the charging box 200 and thuscannot be charged. In a case where the LEDs 205A and 205B arecontinuously lit, this indicates that the charging box 200 is chargingthe portable thermosensitive recording apparatus 120. Blinking at ashort interval attracts user's attention such that the portablethermosensitive recording apparatus 120 is placed at an appropriateposition. Text is displayed on a display 250 such that the user placesthe portable thermosensitive recording apparatus 120 at an appropriateposition. Power transmission is not performed, and thus charging of thesecondary battery is not performed, before the user places the portablethermosensitive recording apparatus 120 at the appropriate position.

When neither of the sensor 230A nor the sensor 230B detects the PC board210 (NO in ACT 160), both of the LEDs 205A and 205B repeatedly blink atthe initial interval of 10 seconds.

Display states of the LEDs 205A and 205B are changed according todetection states in the sensors 230A and 230B, and thus the user candiscriminate states (fast blinking and slow blinking) of the displayunits (LEDs 205A and 205B) and can thus recognize a state of the insideof the charging box 200.

FIG. 9 illustrates examples of the distance D4 between the powertransmission coil 118 and the power reception coil 132, and receivedpower (W) obtained by the power reception device. A transverse axisexpresses the distance D4 between the power transmission coil 118 andthe power reception coil 132. A longitudinal axis expresses the receivedpower (W). Power can be transmitted at the distance D4 of 10 mm to 30mm. Preferably, received power of 20 W or more is obtained in the rangeof the distance D4 of 17 mm to 23 mm. The maximum received power of 26 Wis obtained at the distance D4 of 20 mm. As described above, the PCboard 210 including the power transmission coil 118, and the spacer 232are butted against, via the spring 220, the side surface of the portablethermosensitive recording apparatus 120, and thus the distance D4 can beset to an optimal value. Even in a case where the portablethermosensitive recording apparatus 120 slightly obliquely inserted, thedistance D4 can be maintained while the power transmission coil 118 andthe power reception coil 132 are maintained to be parallel to each otherby elastic force of the spring 220.

The height (H3) of the charging box 200 is provided in accordance withthe height (H1) of the portable thermosensitive recording apparatus 120,and thus a noncontact charging apparatus 50 can be prevented from beingtall. The charging box 200 is made of a metal material. Therefore, thecharging box 200 absorbs noise, and thus radiation noise can be reduced.

The outer surfaces (201A, 201B, 201C, 201D, and 201E) of the chargingbox 200 are made of metal materials and are opaque, and thus the insideof the charging box 200 cannot be seen. A contact state between theportable thermosensitive recording apparatus 120 and the spacer 232cannot be seen, and thus it cannot be checked whether or not theportable thermosensitive recording apparatus 120 and the powertransmission coil 118 are disposed to be separated from each other by anappropriate distance. In the present exemplary embodiment, whether ornot the portable thermosensitive recording apparatus 120 is located atan appropriate position is detected by using the sensors 230A and 230B.In a case where the portable thermosensitive recording apparatus 120 isnot disposed at an appropriate position, the display unit (LEDs 205A and205B) prompts the user to place the portable thermosensitive recordingapparatus 120 at an appropriate position. Therefore, a distance betweenthe power transmission coil 118 and the power reception coil 132 can bemaintained to be constant, and thus power can be transmitted from thecharging box 200 to the portable thermosensitive recording apparatus 120with high efficiency.

Second Exemplary Embodiment

FIG. 10 illustrates a noncontact power transmission apparatus 300according to a second exemplary embodiment. The noncontact powertransmission apparatus 300 includes four charging boxes 200 (310A, 310B,310C, and 310D) of the first exemplary embodiment. The charging boxes310B and 310C are disposed in the Y axis direction. The charging box310A is disposed on the charging box 310B in the gravitationaldirection, and the charging box 310D is disposed on the charging box310C in the gravitational direction. Each of the charging boxes (310A to310D) has an opening 201 in the X axis direction, and allows theportable thermosensitive recording apparatus 120 to be insertedthereinto through the opening 201. The four charging boxes (310A to310D) are integrally fixed to form a charging rack. In the presentexemplary embodiment, four charging boxes (310A to 310D) areexemplified. The present exemplary embodiment is not limited to fourcharging boxes, and more charging boxes may be integrally configured.

The charging boxes (310A to 310D) have the same configuration. Forbetter understanding of an internal configuration of the charging box310A, parts of the case surfaces 201A and 201D in the drawing areremoved. The power transmission coil 118 is disposed on the case surface201E side inside the charging box 310A. A spring 220 is provided betweenthe case surface 201E and the PC board 210 on which the pattern of thepower transmission coil 118 is formed. One end of the spring 220 isfixed to the case surface 201E, and the other end thereof is fixed tothe PC board 210. The spring 220 supports the PC board 210 in aswingable manner.

In the charging box 310A, a case 312A provided with clock input andoutput terminals 314A is provided on the rear surface 201E. Atransmission circuit is provided between the case 312A and the rearsurface 201E. The clock input and output terminals 314A are connected toa power transmission control unit of the transmission circuit.Similarly, the charging boxes (310B to 310D) respectively include clockinput and output terminals (314B to 314D). The clock input and outputterminals (314A to 314D) are operated according to the same clocksignal. In other words, each charging box is operated according to asignal with a phase generated on the basis of a reference clock signal.

Since an operation is performed according to the same clock signal, theoccurrence of noise can be suppressed, and thus stable noncontact powertransmission is possible. The respective charging boxes (310A to 310D)are operated in synchronization with each other, so that phases ofelectric waves transmitted from the respective power transmission coils118 of the charging boxes (310A to 310D) are aligned, and thus theoccurrence of noise can be suppressed.

Each power transmission coil 118 of the charging boxes (310A to 310D) isformed on the Y-Z plane. Magnetic flux generated from the powertransmission coil 118 is generated in a direction orthogonal to thegravitational direction. In other words, magnetic flux generated fromeach power transmission coil 118 is generated in the X axis direction.In a case where the power transmission coil is disposed on the X-Yplane, and the charging boxes overlap each other in the Z axisdirection, magnetic flux generated from the power transmission coil isdirected in the Z axis direction, and thus interference may occurbetween two power transmission coils. In contrast, in the secondexemplary embodiment, it is possible to reduce electric waveinterference among the charging boxes (310A to 310D).

The noncontact power transmission apparatus of the second exemplaryembodiment achieves the same effect as that of the noncontact powertransmission apparatus of the first exemplary embodiment.

In a case where each of the four charging boxes (310A to 310D) chargesthe same type of portable thermosensitive recording apparatus 120, thesame spacer 232 is provided in each of the four charging boxes (310A to310D). The same spacer 232 is not necessarily required to be provided ineach of the four charging boxes (310A to 310D). As an example, a case isassumed in which the charging boxes 310A and 310B charge the portablethermosensitive recording apparatus 120, and the charging boxes 310C and310D charge a portable thermosensitive recording apparatus 121 having acase shape which is different from that of the portable thermosensitiverecording apparatus 120. The above-described spacer 232 is provided inthe charging boxes 310A and 310B, and a spacer formed in accordance withthe case shape of the portable thermosensitive recording apparatus 121is provided in the charging boxes 310C and 310D. Consequently, differenttypes of portable thermosensitive recording apparatuses can besimultaneously charged.

Third Exemplary Embodiment

FIG. 11 illustrates a noncontact power transmission apparatus 400according to a third exemplary embodiment. In the charging box 200 ofthe noncontact power transmission apparatus 400, the PC board 210provided with the power transmission coil 118 is supported by twosprings 222 and 224. The charging box 200 of the third exemplaryembodiment has the same configuration as that of the charging box 200 ofthe first exemplary embodiment except that the springs 222 and 224 areprovided.

The springs 222 and 224 are provided between the case surface 201E andthe PC board 210 on which the pattern of the power transmission coil 118is formed. The power transmission coil 118 may be formed in a squarespiral pattern of two turns. A central line of the Y axis directionwidth W4 of the pattern is indicated by CL1, and a central line of the Zaxis direction height H4 is indicated by CL2. One ends of the springs222 and 224 on the power transmission coil 118 side are fixed onto thecentral line CL2 at symmetric positions with the central line CL1interposed therebetween. The other ends of the springs 222 and 224 onthe case surface 201E side are fixed to the case bottom surface 201Dsuch that the central lines of the springs 222 and 224 are substantiallyparallel to each other.

The springs 222 and 224 support the PC board 210 in a swingable manner.In a case where the portable thermosensitive recording apparatus 120 isinserted into the charging box 200, the portable thermosensitiverecording apparatus 120 is butted against the PC board 210 via a spacer232. In the same manner as in the first exemplary embodiment, even ifthe portable thermosensitive recording apparatus 120 is inserted in aslightly inclined manner, the PC board 210 is butted against theportable thermosensitive recording apparatus 120 by the springs 222 and224. As a result, the power reception coil 132 and the powertransmission coil 118 can be caused to face each other in parallel whilea predetermined distance therebetween is maintained.

In addition to a portable thermosensitive recording apparatus, thenoncontact power transmission apparatus is applicable to a mobile phone,a personal data assistance (PDA), an electric shaver, and the like.

While certain embodiments have been described, these embodiments havebeen presented byway of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A noncontact power transmission apparatuscomprising: an instrument comprising: a first case, a power receptioncoil arranged to generate an induced current due to magnetic flux in afirst direction intersecting a gravitational direction, and a holderconfigured to hold the power reception coil at a predetermined distancefrom an outer surface of the first case in the first case; and a powertransmission device comprising: a conductive second case having anopening into which the instrument is inserted and in which theinstrument is stored, a power transmission coil disposed in the secondcase so as to generate magnetic flux in the first direction, andarranged to generate an induced current in the power reception coil, andan elastic body disposed in the second case, and arranged to maintain adistance between the power transmission coil and the power receptioncoil to be constant, and to support the power transmission coil.
 2. Theapparatus according to claim 1, wherein the instrument is a portablethermosenstive recording apparatus.
 3. A power transmission deviceconfigured to transmit power to an instrument comprising a first case, apower reception coil arranged to generate an induced current due tomagnetic flux in a first direction intersecting a gravitationaldirection, and a holder configured to hold the power reception coil at apredetermined distance from an outer surface of the first case in thefirst case, in a noncontact manner, the device comprising: a conductivesecond case having an opening into which the instrument is inserted andin which the instrument is stored; a power transmission coil disposed inthe second case so as to generate magnetic flux in the first direction,and arranged to generate an induced current in the power reception coil;and an elastic body disposed in the second case, and arranged tomaintain a distance between the power transmission coil and the powerreception coil to be constant, and to support the power transmissioncoil.
 4. The device according to claim 3, further comprising: a firstcapacitor connected to the power transmission coil; a power transmissionunit configured to transmit power via the power transmission coil andthe first capacitor; a sensor configured to detect a position of thepower transmission coil; and a controller configured to control thepower transmission unit according to an output from the sensor.
 5. Thedevice according to claim 3, wherein the power transmission coilincludes a spacer arranged to maintain a distance between the powertransmission coil and the power reception coil in the first direction tobe constant.
 6. The device according to claim 3, wherein a plurality ofthe power transmission devices are provided, at least two of the powertransmission devices are stacked to overlap each other in thegravitational direction.
 7. The device according to claim 6, wherein theplurality of power transmission devices are operated in synchronizationwith each other.
 8. The device according to claim 3, wherein the elasticbody is one of a spring or a rubber.
 9. The device according to claim 3,further comprising: a sensor configured to detect a position of thepower transmission coil.
 10. The device according to claim 9, furthercomprising: a display; and a controller configured to control thedisplay according to an output from the sensor.
 11. The device accordingto claim 10, wherein the controller is configured to control the displayto indicate that the power reception coil is chargeable by the powertransmission coil when the output from the sensor indicates that thepower reception coil and the power transmission coil are at a positionsuitable for noncontact power transmission.
 12. The device according toclaim 10, wherein the controller is configured to control the display toindicate that the power reception coil is not chargeable by the powertransmission coil when the output from the sensor indicates that thepower reception coil and the power transmission coil are not at aposition suitable for noncontact power transmission.
 13. The deviceaccording to claim 10, wherein the sensor comprises a first sensor and asecond sensor, the controller is configured to control the display toindicate that the power reception coil is chargeable by the powertransmission coil when the output from both the first sensor and thesecond sensor indicates that the power reception coil and the powertransmission coil are at a position suitable for noncontact powertransmission.
 14. The device according to claim 10, wherein the sensorcomprises a first sensor and a second sensor, the controller isconfigured to control the display to indicate that the power receptioncoil is not chargeable by the power transmission coil when the outputfrom either the first sensor or the second sensor indicates that thepower reception coil and the power transmission coil are not at aposition suitable for noncontact power transmission.
 15. The deviceaccording to claim 3, wherein the elastic body comprises two springsarranged laterally with respect to each other.
 16. A method of aligninga power reception coil of an instrument with a power transmission coilof a power transmission device, comprising: inserting the instrumentinto a conductive case of the power transmission device; determiningwhether or not the power reception coil and the power transmission coilare at a position suitable for noncontact power transmission based on anindication from a position sensor; and providing noncontact powertransmission from the power transmission coil to the power receptioncoil, when it is determined that the power reception coil and the powertransmission coil are at a position suitable for noncontact powertransmission.
 17. The method of claim 16, further comprising:controlling a display to indicate that the power reception coil ischargeable by the power transmission coil when it is determined that thepower reception coil and the power transmission coil are at a positionsuitable for noncontact power transmission.